This invention relates to a vapor deposition coating apparatus. More particularly it relates to an apparatus in which the ion current density is carefully controlled to improve coating. This control enhances the versatility and enlarges the range of deposition conditions which can be achieved within a single apparatus, so that coatings with very different properties can be deposited in the same equipment. Also, the present invention enables high quality coatings to be deposited in a large volume apparatus improving the coating productivity and component throughput. The deposition apparatus is based upon magnetron sputtering sources in which the ion current driven towards the samples is carefully controlled.
Magnetron sputtering is a very well established technique which is able to produce high quality vapor deposited coatings for a wide range of applications.
A number of improvements in magnetron sputtering have occurred during the last ten years. The first break through was provided by the unbalanced magnetron [B. WINDOWS, N. SAVVIDES, J. Vac. Sci. Technol., A4 (1986) 453] which improved the ion flux escaping the magnetron surrounding so the samples to be coated were subjected to a higher ion bombardment with beneficial effects in the structure of certain types of coatings. Variations in this principle and control modes for the degree of unbalancing have been previously disclosed [W. MAASS, B. CORD, D. FERENBACH, T. MARTENS, P. WIRZ, Patent DE 3812379 Apr. 14, 1988].
In the case of large volume coating apparatus it has been necessary to provide high ionization sources in areas well away from the magnetron. This extra ionization has been implemented by the use of supplementary excitation sources such as radio-frequency and microwave means [M. NIHEI, J. ONUKI, Y. KOUBUCHI, K. MIYAZAKI, T. ITAGAKI, Patent JP 60421/87 Priority Mar. 16, 1988] and the provision of magnetic arrangements next to the magnetron sources [D. G. TEER, Proceedings for the First International Symposium on Sputtering and Plasma Processingxe2x80x94ISSPO91, Tokyo, Japan, February 1991; and A. FEUERSTEIN, D. HOFMANN, H. SCHUSSLER, Patent DE 4038497 Priority Dec. 3, 1990, and S. KADLEC, J. MUSIL, Patent CS4804/89, Priority Aug. 14, 1989; and W. D. Mxc3x9cNZ, F. J. M. HAUZER, B. J. A. BUIL, D. SCHULZE, R. TIETEMA, Patent DE 4017111 Priority May 28, 1990]. All described methods have had a limitation in the maximum chamber size, generally limited to 0.5 to 1 meters in diameter, that can be used for the deposition of a successful coating.
The present invention overcomes such a limitation and can give rise to a novel apparatus which could be up to four meters in diameter.
According to one aspect of the present invention there is provided a vapor deposition coating apparatus comprising a vacuum chamber, at least one coating means or ionization source disposed at or about the periphery of a coating zone, characterized in that the apparatus is provided with one or more internal magnetic means positioned such that magnetic field lines are generated across the coating zone and means for altering the strength or position of the magnetic field lines.
According to a further aspect of the present invention there is provided a multi-station deposition unit comprising a plurality of coating stations each defining a confinement volume, the unit comprising a plurality of coating means or ionization sources disposed at or about the periphery of the coating zone and one or more internal magnetic means positioned such that magnetic field lines are generated across each coating zone and means for altering the strength or position of the magnetic field lines.
According to yet a further aspect of the present invention there is provided a vapor deposition coating method characterised in that magnetic field lines can be regulated across a coating zone by means which enable an ion current density to be controlled.
The apparatus can incorporate a number of coating means of which one is preferably a magnetron cathode which will be situated around the samples to be coated. At or towards the interior of the chamber a single or plurality of means generate a magnetic field. These means could comprise a single or plurality of magnetic polarities which could be the same or different to those of the outer magnetic array of the magnetron source. These magnetic sources provide a means enabling deposition under different ion bombardment conditions to be controlled in different areas of the coating apparatus and/or at different times in the deposition process.
The magnetic strength of these poles could be controlled by different means, e.g. by changing the current of the electromagnet units or by mechanical displacement of the permanent magnetic means or both.
Identical or different magnetron polarities could be used within the same apparatus.
The magnetic strength of the magnetrons could be also varied as could the relative position of the inner and outer magnetic poles.
Auxiliary magnetic poles could be used in the chamber surroundings in order to optimize the plasma confinement. Magnetic confinement enhancement could be achieved by magnetic means which present opposite polarity to the central pole. Also suitable electric currents could provide adequate magnetic confinement by generating magnetic fields for this purpose, especially when they are combined with other magnetic means.
All these magnetic variations make the apparatus versatile in its applications.
Generally, the apparatus will enable maximum magnetic confinement necessary in larger deposition apparatus to ensure high quality coatings. The internal magnetic means could have independent biasing from the samples to be coated. The samples to be coated could be biased or un-biased. The bias applied to the samples to be coated could be powered by direct current (DC) and alternative excitation means at different frequencies such as alternating current (AC) at very low frequencies (1-1000 Hz), or pulsed voltages at low frequencies (Pulsed-LF) (1-1000 KHz), or medium frequency (MF) waves (1-3 MHz),or radiofrequencies (RF) waves (1-1000 MHz), or any combination or modulation of these or other excitation means.
The apparatus could incorporate any other number of means in order to enhance the ionization such as microwaves and/or medium and high frequency devices and means suitable for the generation of glow discharges and ion vacuum techniques such as arcs, hot filament, lasers, electron guns and ion beams.
Larger apparatus, above two meters in diameter can be produced by magnetic linkage between magnetrons and internal poles. Spatial distribution of magnetrons and additional magnetic means could be varied in order to achieve optimization of spaces where magnetic confinement conditions are appropriate for coating depositions. A large coating apparatus could comprise of one or more confinement areas or stations.